The Release 10/11/12 (Rel-10/11/12) of the 3rd Generation Partnership Project Long Term Evolution Advanced (LTE-A) is a technical enhancement of the Release 8/9 (Rel-8/9) of the 3rd Generation Partnership Project Long Term Evolution (LTE). An LTE-A system has a higher bandwidth requirement than an LTE system, and supports a peak data rate up to 1 Gbits/s. In order to meet a requirement of the LTE-A, in the LTE-A system, a carrier aggregation (CA) technology is used as a method for expanding system bandwidth by the LTE-A system, and a multiple-input multiple-output (MIMO) enhancement technology and an adaptive technology are frequently used, so as to improve a data rate and system performance.
In the LTE-A Rel-12, an enhancement for a hotspot area becomes a popular topic. The hotspot area includes an indoor scene and an outdoor scene, and is covered by multiple low-power micro base stations to form a small cell network (SCN). An indoor micro base station supports only user equipment (UE) that moves at a low speed, and an outdoor micro base station supports UE that moves at a low speed and UE that moves at a moderate speed. Neither of the two micro base stations supports UE that moves at a high speed. Generally, it is considered that UE moves at a low speed when a movement speed of the UE is 0-15 km/h, the UE moves at a moderate speed when the movement speed of the UE is 15-60 km/h, the UE moves at a high speed when the movement speed of the UE is above 60 km/h. Because the micro base station serves only UE that moves at a moderate speed and UE that moves at a low speed, and quality of a radio channel between the micro base station and the UE is relatively good, overheads of pilot and control signaling may be reduced. In addition, coverage of the micro base station is less than that of a macro base station, and a quantity of UE served by the micro base station is also less than a quantity of UE served by the macro base station, so that the overheads of pilot and control signaling may be further reduced from this perspective.
In the LTE-A Rel-12 release, the Small Cell Enhancement Work Item (SCE WI) introduces a feature of dual connectivity. That is, UE may be simultaneously connected to at least two base stations, for example, may be simultaneously connected to a macro base station and a micro base station, where the macro base station and the micro base station may be on a same frequency or may be on different frequencies. Because coverage of a micro base station is small, if a movement speed of UE is relatively high, the UE is prone to frequently enter from coverage of one micro base station to coverage of another micro base station, causing frequent handovers between base stations. Dual connectivity may allow the UE to keep connected to a macro base station and a micro base station simultaneously. Content related to mobility management and a real-time service, such as voice over Internet Protocol (VoIP), are provided by the macro base station for the UE, and the micro base station provides only a data service for the UE. The dual connectivity may prevent a case in which the UE is frequently handed over between base stations.
When the UE is connected to at least two base stations, and if the UE has only a single-link transmission capability in an uplink direction, different data cannot be separately sent to the macro base station and the micro base station at the same time. For the UE, a time division multiplexing (TDM) method may be used, and data is sent to different base stations at different time. However, because uplink transmit power required for sending data to the micro base station and uplink transmit power required for sending data to the macro base station have a relatively large difference, the prior art does not disclose how to implement control over uplink transmit power of the UE in the case of dual connectivity.